Studies are being performed to determine the influence of steady-state levels of carbon dioxide tension (PaCO2 from 15 to 100 mmHg) on the response of the intact organism to disturbances of acid-base and electrolyte physiology. BIBLIOGRAPHIC REFERENCES: Gougoux, A., Kaehny, W.D., and Cohen, J.J. Renal adaptation to chronic hypocapnia: dietary constraints in achieving H ion retention. American Journal of Physiology 229: 1330, 1975. Cohen, J.J., Madias, N.E., Wolf, C.J., and Schwartz, W.B. Regulation of acid-base equilibrium in chronic hypocapnia: Evidence that the response of the kidney is not geared to the defense of extracellular (H ion). Journal of Clinical Investigation 57: 1483, 1976.